Synthetic transformations of higher terpenoids: XIX. Synthesis of 1,7-epoxyisoindolones and 7,9a-epoxythiazolo[2,3-a]isoindolones from terpenoids

The reductive amination of methyl 16-formyllambertianate with L-leucine or L-methionine esters resulted in labdanoid furfurylamines whose acylation with maleic anhydride on chlorides of methacrylic or crotonic acids gave the corresponding unsaturated amides that readily entered into the reaction of intramolecular [4+2]-cycloaddition giving the corresponding derivatives of 10-oxa-3-azatricyclo[5.2.1.01,5]dec-8-en-4-one. As a result of a sequence of reactions: The amination of methyl 16-formyllambertianate with cystamine, the acylation of the obtained methyl 16-thiazolidinyllambertianate with the above mentioned acid chlorides or with maleic anhydride, and the intramolecular cyclization of the arising furfurylamine we obtained terpenoid derivayives of 7,9a-epoxyhexahydrothiazolo[2,3-a]isoindol-5-one.